Disposable filter cartridges are widely used for the filtration of a variety of fluids. Generally, such filter cartridges include cylindrically shaped filter media which define a central core chamber. The filter medium is typically provided with appropriate end caps which allow fluid to be forced through the depth of the filter media. Some filter cartridges (e.g., as depicted in FIG. 4 of U.S. Pat. No. 5,681,469) are provided with an integral rigid core structure which provides the filter media with structural support (e.g., so the filter medium is capable of withstanding fluid pressure differentials during use). Other filter cartridges, as shown, for example, in U.S. Pat. No. 5,399,264, employ a relatively rigid, self-supporting, porous, thick-walled tubular filter cartridge element having specially designed flexible end caps. Still other filter cartridges, such as those depicted in U.S. Pat. Nos. 4,218,324 and 5,681,461 employ a "coreless" disposable filter cartridge having rigid preformed end caps. The coreless disposable filter cartridge is sleeved over, and fluid-sealed with respect to, a reusable separate core structure.
Recently, improvements in the so-called "coreless" filter cartridges were proposed by copending U.S. patent application Ser. No. 09/154,522 filed on Sep. 16, 1998 (the entire content of which is incorporated expressly hereinto by reference, and hereinafter referred to as "the '522 application"). In general, the filter cartridge disclosed in the '522 application includes a generally cylindrical filter medium which defines a cylindrically shaped core space, and a pair of rigid, preformed end caps fixed to opposite ends of the filter medium. At least one of the end caps (e.g., the lower end cap) is annular and has an interior cylindrical surface defining an interior space in alignment with the filter cartridge's core space. A truncated generally conically shaped seal skirt is operatively associated with the annular end cap. The filter cartridge of the '522 application is sleeved over a reusable support core structure which includes a base having a truncated conically shaped seal skirt, and a tubular perforated rigid core element fixed at one end to the base. The annular end-cap and the base of the support core structure are removably mechanically coupled to one another, most preferably by being threadably interconnected. In such a manner, the seal skirt is sealingly engaged with the seal skirt of the base.
While the filter cartridge assemblies disclosed in '522 application represent novel improvements to the state of the art, some additional improvements may still be desired, especially in certain end-use applications. For example, in the power generation industry, large filter cartridge arrays housed within relatively large filtration vessels are typically needed in order to purify various process streams. These filter cartridge arrays typically use a guide rod to help center the core of an integral core/filter media cartridge. Once the cartridge is in place, they are secured to a top plate assembly (e.g., via a top stem and cotter pin arrangement). Needless to say, it is quite time consuming to replace all filter cartridges in a given filtration vessel leading to long equipment down times.
What has been needed, therefore, is an improved filter cartridge assembly which is especially adapted to be used in back-flushing filtration operations and/or which has the ability to be quickly removed. It is toward providing such needs that the present invention is directed.
Broadly, the present invention relates to improvements in filter cartridge assemblies whereby unintended threaded uncoupling between the filter cartridge and the base member may be minimized (if not eliminated entirely). More specifically, a filter cartridge assembly according to the present invention is provided with a generally cylindrical filter medium which defines a cylindrically shaped core space, and a pair of end caps fixed to opposite ends of the filter medium. A threaded base member having detent projections receives at least one of the end caps, most preferably the lower end cap. This lower end cap is annular and has an interior cylindrical surface defining an interior space in alignment with the core space. The interior space is also provided with interrupted threads defining detent spaces.
In use, therefore, the lower end cap may be threadably coupled with the threaded base member such that the detent projections are seated in respective ones of the detent spaces. In such a manner, the unintended threaded uncoupling of the lower end cap and the base member is minimized.
In another aspect of this invention, the filter cartridge is most preferably "coreless" and is capable of being sleeved over a permanent, reusable perforated core element. However, the core element is removably insertable within a base member to which the filter cartridge may be coupled. Specifically, one end of the core element is provided with an annular set ring. The set ring is rigidly connected to the exterior surface in surrounding relationship to the core element at a location spaced axially from the one of its ends (e.g., the lower end) towards the other end (e.g., the upper end). In use, the annular set ring provides a seat which bears against the base when the end of the core element is forcibly inserted thereinto.
These and other aspects and advantages of the present invention will become more clear after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof which follow.